Radio-frequency (RF) transmitters and receivers are found in a multiplicity of applications, in particular in the field of wireless communication and radar sensors. In the automotive sector, there is an increasing need for radar sensors which are used in so-called adaptive cruise control (ACC, or Radar Cruise Control) systems. Such systems can automatically adapt the speed of an automobile in order to thus maintain a safe distance to other automobiles traveling in front (and from other objects and pedestrians). Further applications in the automotive sector are, for example, blind spot detection, lane change assist and the like.
Modern radar systems use highly integrated RF circuits which can combine all core functions of an RF front-end of a radar transceiver in a single housing (single-chip radar transceiver), which is often referred to as a monolithic microwave integrated circuit (MMIC). Such RF front-ends usually comprise, inter alia, a voltage-controlled oscillator (VCO) connected in a phase-locked loop, power amplifiers (PA), directional couplers, mixers and analog-to-digital converters (ADC) as well as associated control circuit arrangements for controlling and monitoring the RF front-end.
Modern frequency-modulated continuous-wave (FMCW) radar systems are often multi-input/multi-output (MIMO) systems having a plurality of transmission (TX) and reception (RX) channels. MIMO systems usually comprise a plurality of MMICs which are arranged on a carrier board (PCB, printed circuit board) and must operate in a synchronous manner, wherein each MMIC per se may have a plurality of RX and TX channels. One object may be considered to be the (in-phase) synchronization of an MIMO radar system having a plurality of MMICs.